Furan resins



Patented Oct. 23, 1951 2,571,994 FURAN RESINS Beaumont Thomas,Watertown, N. Y., assignor to Delrac Corporation, Watertown, N.-Y.

No Drawing. Application April 26, 1951, Serial No. 223,141

The present invention is a continuation in part of my copendingapplication, Serial No. 793,519, filed December 23, 1947, now abandoned,and relates 'to non-crazing furan resins and more particularly to furanresins capable of use and storage as a liquid in an intermediate stageof polymerization and capable of being subsequently set to a solidnon-crazing resin. The invention further includes the method of formingsuch product.

Resins of furfuryl alcohol, furfuraldehyde and equal mixtures of suchfurans are known and it has also been proposed to use a small amount offurfuraldehyde as dry catalyst solvent for polymerization of furfurylalcohol. Such resins while hard, tough and workable have had littleutility generally, and particularly in adhesive and coatingcompositions, primarily because of their tendency to crack and craze.

It is accordingly a primary object of the pres-' ent invention to form anon-crazing furfuryl alcohol-furfuraldehyde resin.

It is a further object to produce such resin in an intermediatepolymeric liquid stage capable of use in adhesive and coatingcompositions.

It is a further object to provide methods of forming such products.

In the broad aspect of the present invention I have found that whilefurfuraldehyde, furfuralcohol mixtures and resins formed of suchmixtures in substantially equal proportions form undesirably shrinking,cracking and crazing resins, such mixed resins will, when adjusted inproportions within the limits of 25% to 40% of furfural to 60% to 75% offurfuryl alcohol, exhibit pronounced stability and non-crazingproperties. In the specific aspect I have found a resin mixture of about2 parts of furfuryl alcohol to 1 part of furfuraldehyde to be perfectlystable and exhibit no tendency to craze or crack.

I The resin may be formed to an intermediate liquid stage byinterrupting the polymerization after a short period of reaction. Suchliquid resin may subsequently set by further addition of catalyst.

In forming the partial polymer, the furfuraldehyde in proportion of 25%-40% and the furfuryl alcohol in proportion of 60 %75% are introducedinto a conventional closed pressure-resistant kettle equipped with anagitator, and heating or cooling jacket for alternated introduction ofsteam for heating or water for cooling, whereby the temperature of thereaction may be rapidly controlled by introduction of steam or coldwater into the jacket. A mineral acid, typically hydro- 8 Claims. (Cl.260-675) chloric acid, in proportion of to 4% is added to the mixture inthe kettle. The contents of the kettle are thereafter heated and stirredby introduction of steam into the jacket until a temperature of about190 F. is reached, whereupon the reaction begins and runsexothermically' and rapidly. The temperature is allowed to reach. therange of 240 to 275 F., but in no case allowed to exceed the upper limitto avoid sub-- stantially complete polymerization of some of thecomponents of the reaction mixture. Upon reach-* ing this range, thetemperature is quickly cut back to the range of about 200 to 230 andheld at such lower temperature range to temper the intermediate resinfor a short period of time of about 5 to 45 minutes, variable with theexact intermediate temperature selected. Thus, at about 220 F. thepartial polymer will be tempered for about 30 minutes, and at about 200F. the partial polymer would be tempered for about 45 minutes, and at ahigher temperature of about 230 F. the partial polymer would be temperedfor 5-10 minutes.

Another check upon the degree of tempering is the viscosity of thepartial polymer produced. Thus, it is suitable to temper the partialpolymer at the intermediate temperature until the liquid resin has aviscosity in the approximate range of 250 to 1000 cps. at F.

The liquid resin is useful in coating compositions, with or withoutplasticizers, and may be applied without heat, with good adhesion toseel, wood or concrete, setting by exposure to air. The film has goodmoisture and chemical resistance both to strong acids and alkalies and.will not shrink, craze, strip or flake off. The liquid resin may alsobe set by addition of various generally acid type catalysts, with orwithout the use of filler materials. Such catalysts may be various acidsor acid-reacting substances such as sulfuric, hydrochloric or phosphoricacids used in quantities of less than 4% and generally about .1% inconcentrated form.

The following example will illustrate a typical procedure for formingthe liquid resin.

Example I 25 gallons of furfuryl alcohol and 12.5 gallons of furfuralare introduced into a closed jacketed kettle equipped with an agitator.2 0 ml. of concentrated hydrochloric acid are slowly added to theagitated mass. The kettle is heated with steam circulated through thejacket. When the temperature of F. is reached, the steam is cut ofi andthe temperature of the agitated mass rises exothermlcally by thevigorous reaction which sets in. After the initial reaction has started,the temperature is controlled by passing cooling water through thekettle jacket, and by varying the rate of flow therethrough, any desiredtemperature may be maintained in the kettle. Slight temperature controlis begun when the initial temperature reaches 200 to 210 F., but thetemperature is allowed to rise. When it reaches the range of 240 to 275F., it'is quickly cut back to 220 F. by increasing the flow of coolingwater. The reaction mass is held and tempered at 220 untfl the viscosityof the liquid partially polymerized resin reaches a desired viscositygenerally about 500 cps. This tempering period is usually less thanminutes. After the desired viscosity has been reached, the reaction isquickly quenched, cooling with very rapid flow of coolingwater to normaltemperatures. The total time including the warming up, reaction,tempering and cooling periods is from 20 to 30 minutes. It will beunderstood that the reaction will proceed rapidly with rapid evolutionof heat and the resin will warm up. The temperature must not be-allowedto exceed 275 F. or the resin will set immediately to a solid. PressuresWill build in the closed kettle during the reaction but such pressure isprevented from exceeding pounds per square inch by venting. Water formedduring the reaction will separate in a layer from the resin and isremoved.

Example II The liquid resin prepared as described in Example, I isapplied as a, coating to steel, wood or concrete. In the case of thewood and concrete the resin will penetrate into the porous surface.After 6 to 24 hours, depending on the porosity of the surface, the resinsets to give a non-tacky, strQngly adherent, non-crazing film. The film'is acid and alkali-resistant. Application of heat will accelerate thesetting time.

Example I II The liquid resin of Example I is treated by adding 2% byweight of concentrated hydrochloric acid added drcpwise thereto andmixed. The resin is then applied as a coating and sets in 45 minutes toa permanent non-crazing film. The setting may be accelerated by heat.

Example IV The liquid resin of Example I is treated by adding 2' to 4%by volume of a saturated solution of ferric chloride in alcohol addedwith mixing. The resin is then applied as a coating and sets withinthirty minutes to a permanent noncrazing film.

Example V The liquid resin treated with acid, or other acid solution, asin Examples III and IV, is pumped as grouting filling to fill the spacesbetween a concrete wall and a brick lining and sets to a hard,non-cracking, chemically-resistant; and strongly adherent filling;material.

Example VI The liquid resin of Example I, further treated with acid, oracid reacting substances, as, in Ex amples III and IV, is cast with orWithout filling materials into molds of various shapes and forms toughnon-crazing, non-cracking resinous bodies that may be readily machined.

Various modifications may be made within the spirit of the presentinvention and it is intended that the examples given be regarded asillustrative and not limiting and the invention be interpreted asbroadly as defined in the claims.

I claim:

1. Method of forming a liquid furan resin comprising adding less than 4%of a mineral acid catalyst to a mixture comprising 60-75% of furfurylalcohol and 25-40% of furfuraldehyde by volume, heating the mixture toinitiate the reaction, quickly cooling the reaction mixture after atemperature within the range of 240 to 275 F. is reached to atemperature in the range of about 200 to 230 F. and holding the reactionmixture at such intermediate temperature until a viscous fluid mass isobtained, and then quenching the reaction by cooling to normaltemperatures.

2. Method of forming a liquid furan resin comprising adding less than 4%of a mineral acid catalyst to a mixture comprising 60%-75% of furfurylalcohol and 25%-40% of furfuraldehyde by volume, heating the mixture toinitiate the reaction, quickly cooling the reacting mixture after atemperature within the range of 2l0-275 is reached to a temperatureabout 220 F., and holding the reaction mixture at such intermediatetemperature until a viscous fluid mass is obtained and then quenchingthe reaction by cooling to normal temperatures.

3. A substantially dry, stable liquid furan resin capable of setting inair to a solid, non-crazing resinous film, said liquid resin beingformed by the method defined in claim 1.

4. A substantially dry, stable liquid furan resin capable of setting inair to a solid, non-crazing resinous film, said liquid resin beingformed by partially polymerizing a mixture of substantially two parts offurfuryl alcohol and one part of furfuraldehyde by volume, according tothe procedure defined in claim 1.

5. The method of forming a completely polymerized non-crazing, solidfuran resin comprising distributing the resin formed in the methoddefined in claim 1 in films exposed to air and allowing the same to set.

6, The method of forming a completely polymerized non-crazing, solidfuran resin comprising adding an additional small quantity of a mineralacid catalyst to the liquid resin formed by the method defined in claim1.

7. A stable, non-crazing, solid furan resin formed by completelypolymerizing the liquid partial polymer formed by the method definedinclaim 1., I

8'. Method of forming a liquid furan resin comprising adding less, than4% of an acid catalyst toa mixture comprising 60% to of furfurylalcohol, and 25% to 40% of furfural'dehyde' by volume, heating toinitiate the reaction, controlling the temperature oi the. reacting massto prevent a temperature of 275 F. and cooling to normal temperature inatotal heating and cooling cycle of less than. 3.0: minutes.

BEAUMONT THOMAS.

No references cited.

1. METHOD OF FORMING A LIQUID FURAN RESIN COMPRISING ADDING LESS THAN 4%OF A MINERAL ACID CATALYST TO A MIXTURE COMPRISING 60-75* OF FURFURYLALCOHOL AND 25-40% OF FURFURALDHYDE BY VOLUME, HEATING THE MIXTURE TOINITATE THE REACTION QUICKLY COOLING THE REACTION MIXTURE AFTER ATEMPERATURE WITHIN THE RANGE OF 240* TO 275* F. IS REACHED TO ATEMPERATURE IN THE RANGE OF ABOUT 200* 230 F. AND HOLDING THE REACTIONMIXTURE AT SUCH INTERMEDIATE TEMPERATURE UNTIL A VISCOUS FLUID MASS ISOBTAINED, AND THEN QUENCHING THE REACTION BY COOLING TO NORMALTEMPERATURES.